There are thousands of wine grape varieties, and 10,000 names for these varieties, though of these only fifty or so are commonly made into wine, with perhaps ten named on bottles in the local wine store. Swift advances have been made in scanning plant genomes so shortly we will know much more about the relationships between all of these varieties (also termed cultivars).

Indeed a big advance has just appeared in the Proceedings of the National Academy of Science, US; 'Genetic Structure and Domestication History of the Grape', by Sean Myles et al, January, 18th. One of the many things that makes the vine interesting is that should something unusual happen to a vine which seems potentially valuable, it is easy to isolate and grow this variation simply by planting a few cuttings after the winter pruning. Or in the words of Myles; "spontaneous somatic mutations captured through vegetative propagation". And this 'new variety' can be kept pure almost indefinitely by simply Progress planting more cuttings and of course using these to replace vines that die.

Myles found that the US Department of Agriculture had 1009 plasma samples of domesticated grapes split between table grapes and wine grapes. His group of researchers has developed a 'chip' which can quickly scan for genetic variations by focussing on a range of key features which when analysed reveals whether a variety has a close or distant relationship to another variety. Thus; "our analyses reveal extensive clonal relationships among cultivars (varieties) and a complex pedigree structure within vinifera that are the result of widespread vegetative propagation."

Of the 1009 they found 75% were related to each other which apparently was a surprise as instead of many families this meant all of the varieties were one large family with the main difference being, 'table grapes connecting to table grapes and wine grapes to wine grapes'. From this number they decided that 583 were unique Vinifera varieties or cultivars.

For many reasons it is hard to make an 'accurate genealogical reconstruction', but "we used patterns of identity-by-descent (IBD) and predictions of population genetic theory to infer simple pedigree relationships among the 583 unique vinifera cultivars that
remained after excluding clonal relationships." Indeed 75% (=384) are related to at least one other variety, in essence a giant family tree though split into two halves, table and wine grapes with some links between the two.

This is depicted in the following diagram:
Figure1. The lone dots have no first degree relatives. The interconnected network includes 384 varieties that are interconnected by a series of first degree relationships out of 583 varieties.

Myles points out that a small number of varieties are highly connected in the network and are thus likely to represent ancient cultivars widely used during grape breeding. For example pinot and gouais blanc are the parents of a further 16 French cultivars. A part of this intricate branching looks like this:
Figure 2. A group of 57 varieties showing the complex relationships between the varieties many of which are very familiar. Observe the focal point of traminer from which an intricate web spreads. Click to enlarge

Of enormous interest is the parent daughter relationship of traminer and pinot noir. Who would ever have thought these varieties had any connection at all. This poses many problems and I doubt if it is the last word.

Also from Figure 2 note the two varieties flora and taminga, as these were developed by the CSIRO, the result of a program to make varieties more suited to the Australian climate. These and several others have not met with acceptance in Australia possibly due to the very inward looking nature of producers and consumers who are wary of change. I also have a suspicion this type of breeding is disliked by a purist wine elite who see experiments like this as interfering with the natural order of nature. Brown Bros is the one company that thrives on difference.

Myles makes the point that much of the diversity is due to vegetative propagation (taking a cutting) not by breeding though a small number of varieties, being highly connected are likely to represent ancient varieties widely used during grape breeding. Or; "We propose that this pedigree structure is the result of a limited number of crosses made among elite
cultivars that were immortalized and sometimes vegetatively propagated for centuries."
Myles strongly believes that wine grape growers, possibly for thousands of years, have been content with vegetative propagation (this is less so with table grapes) and there has not been enough breeding to develop new cross breeds varieties.

Still much of this is puzzling as when we last discussed vines and genes at The Origin of White Wine Varieties
scientists at the CSIRO had advanced the view that about 3000 years ago, two genes that controlled colour in grapes had mutated, in effect turned off, allowing the development of white varieties. Thus all of the white varieties have a single origin from this one new parent variety.

The key conclusions of the CSIRO scientists were:

"Specifically, Dr Mandy Walker and her team showed that the colour of grape skins is controlled by two genes, VvMYBA1 and VvMYBA2.
They found that either gene can regulate the colour by switching on production of a molecule called anthocyanin, which turns grape skin red.
In white grapes, both the genes are mutated, meaning both ways for producing a red colour were switched off.
"This was a lucky coincidence for all the white wine drinkers around the world," Dr Walker says.
"Mutations in single genes happen at a fairly low frequency, but the grapes had to have mutations in two genes to turn from red to white and that's just very, very rare."

The researchers studied more than 55 different strains of white grape and shown that all of them contained both mutations.
"We took grapes from as many different regions of the world as possible, and the changes were all the same," she says.
This evidence suggests that all the white grape varieties have a single genetic ancestor."

The new research would seem to challenge this assumption as it suggests all the varieties are in a giant three dimensional array and not two separate halves, red or white, as the CSIRO research suggests.

Myles view that cross breeding should be encouraged vindicates the CSIRO and the main researcher, Alan Antcliff, and this type of research should be resumed as Myles contends that all manner of genes can be enhanced to make the vine, for example more disease resistant and for Australia more drought resistant.

For drinkers there may be untold delights ahead and just think of a relatively recent cross, possibly dating to the 14th Century, between cabernet franc and sauvignon blanc which lead to cabernet sauvignon.

I also had always thought the evolution of pinot was relatively recent, perhaps the 11th Century, though this research suggests its origins might go back much further. It would also seem that varieties often found together in old world wine-scapes means they have a similar origin. For example the authors find a close genetic link between shiraz and viognier, which are both associated with the Rhone Valley.

It is apparent that the mysteries of the genetic relationships of the thousands of varieties will unfold over the next decade. This leaves us with today's problem which is how pinot, a royal variety, could have a parentage linked back to traminer. This is like finding your favourite friend had an alien as a parent. Strange but likely true.

Friday, 20th August, 2004

Thursday, 19th August, 2004

Wednesday, 23rd June, 2004

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